1. Field of the Invention
This invention relates to magnetic recording reproducing systems, and more particularly to a system which is able to provide a recording bias current optimum for various magnetic tapes different in characteristic.
2. Description of the Prior Art
Generally stated, the value of optimum recording bias current for a magnetic tape used with tape recorders or the like differs with various factors such as quality, shape, thickness of coating, and the like of a magnetic material coated on the tape. However, in order to obtain favourable recording-reproducing characteristics there is required an optimum recording bias current irrespective of the type of magnetic tape. In the past, therefore, low frequency signals (such as, for example, 400 Hz or 1 KHz) have been used to effect recording while manually varying the recording bias current, thereby providing an optimum value, that is, the most sensitive bias current which achieves the highest reproducing level or the recording bias current slightly greater than the bias as described above.
Illustrative examples of apparatus known to automatically determine the bias current are disclosed in U.S. Pat. No. 2,791,640, wherein the bias current is varied to render the frequency characteristic flat. In the apparatus disclosed in the aforesaid patent, however, the bias current determined thereby is not always optimum in value for the dynamic range and distortion factor.